Wafer Level Packaging (WLP) refers to the technology of packaging an integrated circuit (IC) at a wafer level, instead of the traditional process of assembling the package of each individual die on individual packages. One feature of the WLP is that the resulting integrated circuit package is practically the same size as the individual package diced. Furthermore, WLP provides a streamlining of the semiconductor manufacturing process from start to customer shipment.
After forming the package on the wafer level, a single processed package wafer in WLP is separated into individual packages with finished interconnection and device protection over the die or dies. This separation process is called singulation and is typically carried out by a mechanical or laser saw traversing through the narrow bands between adjacent packages.
Passing the mechanical or laser saw through the narrow bands exerts mechanical stresses to the package wafer. The saw-cut induced stresses can variously manifest as cracking, chipping, flaking, peeling, and/or delamination of the layered semiconductor materials at the edges of the dies or chips. Other issues such as cutting precision also adversely affects package reliability and production yield. The problem is more acute in WLP because most of the integration or packaging steps are completed before singulation, any mis-operation or structural damage at this point wastes cost and effort of all preceding steps. Improvements on methods or structural design which increase the yield of singulation continues to be sought.